Core Machine

ABSTRACT

Core machine intended particularly to the oil prospection field, comprising a core crown (2), an external tube (3) for the rotational driving of the core crown (2), and an internal tube (4) having a free front end element (7) intended to receive a core (5), and a revolution surface (8) of the free end element (7) on the crown side (2), arranged to cooperate with an internal surface (9) thereof, or optionally of the external tube (3), so as to adjust between the two a predetermined passage for the core drilling fluid, the free end element (7) being mounted in the core drilling machine (1) so as to slide coaxially on an extremity section (13) of the internal tube (4), between a position wherein the revolution surface (8) is in contact with the internal surface (9) of the crown (2), or respectively of the external tube (3), and an extreme position away from said internal surface (9).

BACKGROUND OF THE INVENTION

The present invention relates to a core sampler, particularly in thefield of oil prospecting, comprising:

a core-sampling ring,

an outer barrel for rotating the sampling ring, and

an inner barrel which has a free front end element and is intended toaccommodate a core sample during sampling, the inner and outer barrelsbeing more or less coaxial, and

a surface of revolution of the free end element, on the same side of thering, designed to interact with an internal surface of the latter, or,if appropriate, of the outer barrel, so as together to set apredetermined passage for core-sampling fluid.

In the case of a core-sampler of this kind, the free end element of theinner barrel has a circular lip parallel to the longitudinal axis ofrotation and situated in an annular housing in the ring, which alsoextends parallel to the longitudinal axis of rotation. Regulating thepassage for fluid herein proves tricky, for example given that the innerbarrel is fixed to the outer barrel a great distance away from theposition of this passage and given the significant variations in lengthwhich may occur in a core sampler on account of the variable and hightemperatures that the latter may experience during sampling. To date,the operator assembling a core sampler tries to obtain a correct settingof this passage by taking account of the differences in length exhibitedby the various portions of the inner and outer barrels, and by takingaccount of the temperatures which it is assumed are reached during coresampling. It is, however, known that in practice the passage actuallyobtained may be too different from the one anticipated. Furthermore, theinner barrel may be made of a different material (for example glassfibre coated with a binder) from that of the outer barrel, which isusually made of steel, and the differential expansions that these twobarrels undergo oppose the obtaining and/or maintaining of the desiredsetting for the fluid passage. Furthermore, a core sample entering theinner barrel may push the latter slightly towards the top of the outerbarrel, depending on the play in the thrust ball bearings or ballbearings which connect the inner and outer barrels, and this may changethe aforementioned setting appreciably.

In either event, poor setting of the said passage may lead, for example,to an excessive flow rate of sampling fluid towards the core sample andto a possibly deep adverse alteration thereof by washing, etc., or may,for example, lead to excessive contact between the said surface ofrevolution of the free end element and the internal surface of the ringor of the outer barrel, leading to seizure of these surfaces as onerotates with respect to the other, or to deformation and/or breakage ofthe free end element, etc.

The object of the present invention is to overcome the aforementioneddrawbacks, and others which are not explained hereinabove but are knownto those skilled in the art, and to provide a means that makes itpossible simply and reliably to obtain the correct regulation, evenregulation down to zero or almost zero passage for the core-samplingfluid between the free end element of the inner barrel and thecorresponding internal bearing surface, without troublesome pressure ofone on the other, and therefore without the aforementioned risks ofseizure, deformation or breakage at this point.

To this end, according to the present invention, the free end element ismounted in the core sampler in such a way that it can slide coaxiallyover an end portion of the inner barrel, between a position in which thesurface of revolution is in contact with the internal surface of thering or of the outer barrel, respectively, and an extreme position awayfrom this internal surface.

In one embodiment of the invention, the sliding free end element and theend portion each comprise a stop, which stops interact with one anotherwhen the inner barrel is withdrawn from its core-sampling position inthe outer barrel, so as to lock the free end element on the end portionin another extreme position situated beyond the said contact positionstarting from the extreme position away from the internal surface.

Other details and particular features of the invention will emerge fromthe secondary claims and from the description of the drawings which areappended to this text and which illustrate, by way of non-limitingexamples, some embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts diagrammatically in axial section, a length of a coresampler equipped in accordance with the invention.

FIG. 2 diagrammatically depicts, on a different scale, in axialhalf-section, a length of another core sampler equipped in accordancewith the invention.

DETAILED DESCRIPTION

In the various figures, the same reference notation is used to denoteelements which are identical or analogous. To improve the clarity of thedrawings, some elements of the core sampler have been depicted by theiroutline in chain line and without hatching.

The core sampler 1 in FIG. 1 has a sampling ring 2 mounted on an outerbarrel 3, intended, among other things, for rotating the ring 2, and aninner barrel 4, intended to receive a core sample 5 during acore-sampling operation. A split frustoconical ring 6 is provided in theinner barrel 4 and is intended to lock a core sample therein. The inner4 and outer 3 barrels are each formed of various lengths of barrel fixedtogether, for example by screwing, and are practically coaxial. Theinner barrel 4 has a free front end 7, when considering the direction offorward travel of the core sampler 1 during a core-sampling operation.This free end element 7 is delimited by a surface of revolution 8designed to interact with an internal surface 9 of the ring 2 or, asappropriate, of the outer barrel 3 in a mutual arrangement of these twocomponents mounted one on or in the other, so as to regulate, betweenthe surface of revolution 8 and the internal surface 9, a predeterminedpassage for core-sampling fluid.

In the case of FIG. 1, the core-sampling fluid is conveyed through anannular duct 10 delimited by the inner 4 and outer 3 barrels, so as toend up at the bottom of a core-sampling hole via nozzles 11 in the ring2. It may be desirable for a small amount of core-sampling fluid to beable, however, to pass directly from the annular duct 10 as far as a gap12 between a core sample 5 and the ring 2, so as to lubricate and coolthis point of friction between these two components. These flow of fluidto this gap must, however, be limited so as to prevent this fluid fromadversely affecting the core sample produced.

To achieve this, and for the reasons explained earlier, the free endelement 7 is mounted in the core sampler 1 in such a way that it canslide coaxially over an end portion 13 of the inner barrel 4, between aposition in which the surface of revolution 8 is in contact with thesaid internal surface 9 and an extreme position away from this internalsurface 9.

In the embodiment of FIG. 1, the free end element 7 ends in a groove 14which extends parallel to the longitudinal axis of the core sampler 1and which, in its bottom, comprises the internal surface 9 for thebearing of the surface of revolution 8.

In the embodiment of FIG. 2, the free end element 7 ends against aninternal surface 9 of the ring 2 and the end portion 13 has another freeend element 15 fixed to it and which, in the core-sampling position inthe core sampler 1 can project from the sliding free end element 7.

The sliding set-up can be adjusted so that the pressure of thecore-sampling fluid, acting on the surfaces of the free end element 7,presses the surface of revolution 8 and the internal surface 9 againsteach other. The pressing force can be considered as being low given thesmall amount of surface area that the free end element 7 presents or canpresent to the fluid pressure. This pressing force may, however, beincreased by known hydraulic means (pressure drops, for example, and/orincrease in flow rate) to prevent the free end element 7 from beingpushed upwards, for example by core-sample debris passing between thering 2 and the end length 13.

According to the drawings of FIGS. 1 and 2, the contact between thesurface of revolution 8 and the internal surface 9 may be continuous andthe passage for fluid through the annular duct 10 towards the gap 12 isthen practically closed. It is, however, possible, for example, to equipthe free end element 7 with calibrated passage holes (not depicted) orcalibrated cuts (not depicted) made in the surface of revolution 8 inorder to allow a predetermined flow rate of fluid (depending on thefluid pressure) to pass.

The sliding free end element 7 may furthermore be mounted so that it canturn on the end length 13. This, for example, allows the wear due tofriction as the outer barrel 3 rotates with respect to the inner barrel4 to be spread between the point of contact between the surface ofrevolution 8 and the internal surface 9, and the point of contactbetween the free end element 7 and the end length 13, or alternatively,allows this wear to be transferred to the latter point, the componentsof which are, for example, removable and replaceable.

For this reason, at least the said end length 13 may be fitted on therest of the inner barrel 4 removably.

The free end elements 7 and end length 13 may be made of differentmaterials from the inner barrel 4, outer barrel 3, and ring 2 and beselected on the basis of the friction they are to experience.

As a preference, the free end element 7 and the end length 13 eachcomprise a stop 20, 21 interacting with one another, when the innerbarrel 4 is withdrawn from its core-sampling position into the outerbarrel 3. The stops 20, 21 interact in such a way as to lock the freeend element 7 on the said end length 13 in another extreme position (notdepicted) situated away from the said position of contact between thesurface of revolution 8 and the internal surface 9 with respect to thefirst mentioned extreme position away from the internal surface 9.

Advantageously, the end portion 13 may comprise, by way of a stop 20, onthe side that is towards the bottom of the well in the samplingposition, an external cylindrical collar 22 and, between this and therest of the inner barrel 4, a cylindrical body 23 of smaller outsidediameter than the external cylindrical collar 22. The free end element 7then comprises, on the same side as this same well bottom, an open-endedcylindrical hole 24, the inside diameter of which is adapted to theoutside diameter of the external collar 22 for the purpose of theaforementioned sliding and, on the opposite side to the well bottom, byway of a stop 21, an internal cylindrical collar 25, the inside diameterof which is smaller than that of the cylindrical hole 24 and which isadapted to the outside diameter of the cylindrical body 23 with a viewto the said sliding.

It must be understood that the invention is not in any way restricted tothe embodiments described and that many modifications can be made to thelatter without departing from the scope of the present invention.

Thus, in the core sampler according to the invention, the arrangementwhereby the end portion 13 is mounted on the rest of the inner barrel 4so that it can be removed, may consist, for example, of an assembly withan external screw thread on the end portion 13, on its end away from thewell bottom, and an internal screw thread on the corresponding end ofthe rest of the inner barrel 4. As a preference, the external screwthread has a diameter at most equal to the outside diameter of thecylindrical body 23 and, when the screw threads are cylindrical, theyare advantageously left-hand threads.

A seal 30 may be mounted, for example, in the internal surface of theinternal cylindrical collar 25 so as to interact with the externalperipheral surface of the cylindrical body 23 and thus improvesampling-fluidtightness at this point.

The core sampler 1 of the invention advantageously comprises a splitfrustoconical ring 6 as depicted in FIG. 1 and having a V-shaped cut 33where it is split, an internal cylindrical surface 34 which has beenroughened, in the known way, in order to catch on a core sample 1, and agrooved external frustoconical surface 35.

One or more notches 40 may be provided on a face of the free end element7 which faces towards the rest of the inner barrel 3. These notches 40may be used for detaching, possibly through fluid pressure, one element7 with respect to the said remainder of the inner barrel 3.

Notches 41 may be provided on the end face of the unscrewable end length13, so as to take a tool for screwing or unscrewing this length 13.

What is claimed is:
 1. Core sampler, particularly in the field of oilprospecting, comprising:a core-sampling ring (2), an outer barrel (3)for rotating the sampling ring (2), and an inner barrel (4) which has afree front end element (7) and is intended to accommodate a core sample(5) during sampling, the inner (4) and outer (3) barrels being more orless coaxial, and a surface (8) of revolution of the free end element(7), on the same side of the ring (2), designed to interact with aninternal surface (9) of the latter, or, if appropriate, of the outerbarrel (3), so as together to set a predetermined passage forcore-sampling fluid,characterized in that the free end element (7) ismounted in the core sampler (1) in such a way that it can slidecoaxially over an end portion (13) of the inner barrel (4), between aposition in which the surface (8) of revolution is in contact with theinternal surface (9) of the ring (2) or of the outer barrel (3),respectively, and an extreme position away from this internal surface(9).
 2. Core sampler according to claim 1, characterized in that thesliding free end element (7) is mounted so that it can turn on theaforementioned end portion (13).
 3. Core sampler according to claim 1,characterized in that the sliding free end element (7) and the endportion (13) each comprise a stop (20, 21), which stops interact withone another when the inner barrel (4) is withdrawn from itscore-sampling position in the outer barrel (3), so as to lock the freeend element (7) on the end portion (13) in another extreme positionsituated beyond the said contact position with respect to the extremeposition away from the internal surface (9).
 4. Core sampler accordingto claim 1, characterized in that the said end portion (13) is designedso that it can be removed from the rest of the inner barrel (4).
 5. Coresampler according to claim 4, characterized in that the end portion (13)comprises, by way of a stop (20), on the side that is towards the bottomof the well in the sampling position, an external cylindrical collar(22) and, between this and the rest of the inner barrel (4), acylindrical body (23) of smaller outside diameter than the externalcylindrical collar (22) and in that the free end element (7) comprises,on the same side as this same well bottom, an open-ended cylindricalhole (24), the inside diameter of which is adapted to the outsidediameter of the external collar (22) for the purpose of theaforementioned sliding and, on the opposite side to the well bottom, byway of a stop (21), an internal cylindrical collar (25), the insidediameter of which is smaller than that of the cylindrical hole (24) andwhich is adapted to the outside diameter of the cylindrical body (23)with a view to the said sliding.
 6. Core sampler according to claim 4,characterized in that the arrangement whereby the end portion is mountedon the rest of the inner barrel (4) so that it can be removed, consistsof an assembly with an external screw thread on the end portion (13), onits end away from the well bottom, and an internal screw thread on thecorresponding end of the rest of the inner barrel (4), in that, as apreference, the external screw thread has a diameter at most equal tothe outside diameter of the cylindrical body (23) and in that, when thescrew threads are cylindrical, they are advantageously left-handthreads.
 7. Core sampler according to any one of claim 1, characterizedin that it comprises pressure responsive hydraulic pressing meansdesigned to act on the free end element (7) so as to press the surface(8) of revolution onto the internal surface (9) with a controlled force.8. Core sampler according to claim 2, characterized in that the slidingfree end element (7) and the end portion (13) each comprise a stop (20,21), which stops interact with one another when the inner barrel (4) iswithdrawn from its core-sampling position in the outer barrel (3), so asto lock the free end element (7) on the end portion (13) in anotherextreme position situated beyond the said contact position with respectto the extreme position away from the internal surface (9).
 9. Coresampler according to claim 2, characterized in that the said end portion(13) is designed so that it can be removed from the rest of the innerbarrel (4).
 10. Core sampler according to claim 3, characterized in thatthe said end portion (13) is designed so that it can be removed from therest of the inner barrel (4).
 11. Core sampler according to claim 5,characterized in that the arrangement whereby the end is mounted on therest of the inner barrel (4) so that it can be removed, consists of anassembly with an external screw thread on the end portion (13), on itsend away from the well bottom, and an internal screw thread on thecorresponding end of the rest of the inner barrel (4), in that, aspreference, the external screw thread has a diameter at most equal tothe outside diameter of the cylindrical body (23) and in that, when thescrew threads are cylindrical, they are advantageously left-handthreads.
 12. Core sampler according to claim 2, characterized in that itcomprises pressure responsive hydraulic pressing means designed to acton the free end element (7) so as to press the surface (8) of revolutiononto the internal surface (9) with a controlled force.
 13. Core sampleraccording to claim 3, characterized in that it comprises pressureresponsive hydraulic pressing means designed to act on the free endelement (7) so as to press the surface (8) of revolution onto theinternal surface (9) with a controlled force.
 14. Core sampler accordingto claim 4, characterized in that it comprises pressure responsivehydraulic pressing means designed to act on the free end element (7) soas to press the surface (8) of revolution onto the internal surface (9)with a controlled force.
 15. Core sampler according to claim 5,characterized in that it comprises pressure responsive hydraulicpressing means designed to act on the free end element (7) so as topress the surface (8) of revolution onto the internal surface (9) with acontrolled force.
 16. Core sampler according to claim 6, characterizedin that it comprises pressure responsive hydraulic pressing meansdesigned to act on the free end element (7) so as to press the surface(8) of revolution onto the internal surface (9) with a controlled force.